ffmpeg static class fails to initialize on mobile.

[emmauss]

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• Do you want to request a feature or report a bug?
  Report a bug

• What is the current behavior?
  ffmpeg static class fails to initialize on non desktop platforms, eg. Android. The line where it throws a PlatfromNotSupportedException is,

  FFmpeg.AutoGen/FFmpeg.AutoGen/FunctionResolverFactory.cs

  Line 15 in 534a3eb

  throw new PlatformNotSupportedException();

• *If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem:

• What is the expected behavior?

• What is the motivation / use case for changing the behavior?

• Please tell us about your environment:

• version: 6.0. dotnet 7 Android

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, gitter, etc)

[Ruslan-B]

I wonder what PlatformID you are getting to make it fail.
You can try to workaround by setting DynamicallyLoadedBindings.FunctionResolver = new LinuxFunctionResolver(); before calling DynamicallyLoadedBindings.Initialize().
Please, let me know upon result.

[emmauss]

GetPlatformId is called here,

FFmpeg.AutoGen/FFmpeg.AutoGen/FFmpeg.cs

Line 17 in 15d15bd

EAGAIN = FunctionResolverFactory.GetPlatformId() switch

, in the static constructor. I don't think it can be bypassed.

[emmauss]

StackTrace

at FFmpeg.AutoGen.FunctionResolverFactory.GetPlatformId()
at FFmpeg.AutoGen.ffmpeg..cctor()

[emmauss]

Although my projects are all Net7, the autogen nuget package is net standard 2.0.

[Ruslan-B]

Right, I see. I'll do hotfix.

[emmauss]

I wonder what PlatformID you are getting to make it fail. You can try to workaround by setting DynamicallyLoadedBindings.FunctionResolver = new LinuxFunctionResolver(); before calling DynamicallyLoadedBindings.Initialize(). Please, let me know upon result.

I switched to using DynamicallyLoadedBindings, and the previous error no longer occurs.
Instead it fails on dlopen, as libdl doesn't exist on android,

FFmpeg.AutoGen/FFmpeg.AutoGen.Bindings.DynamicallyLoaded/Native/LinuxFunctionResolver.cs

Line 14 in 534a3eb

protected override IntPtr LoadNativeLibrary(string libraryName) => dlopen(libraryName, RTLD_NOW);

[Ruslan-B]

Well, I guess you are the first one how trying this on android.
You can create a copy of LinuxFunctionResolver with this thing private const string Libdl = "libdl.so"; - i.e. without version suffix.

[Ruslan-B]

I switched to using DynamicallyLoadedBindings, and the previous error no longer occurs. Instead it fails on dlopen, as libdl doesn't exist on android,

Question here from which set of bindings did you switched?

[emmauss]

I switched to using DynamicallyLoadedBindings, and the previous error no longer occurs. Instead it fails on dlopen, as libdl doesn't exist on android,

Question here from which set of bindings did you switched?

I was using the legacy Autogen. I'm modifying an existing library to work on android, and it was made a while ago.

[Ruslan-B]

I switched to using DynamicallyLoadedBindings, and the previous error no longer occurs. Instead it fails on dlopen, as libdl doesn't exist on android,

Question here from which set of bindings did you switched?

I was using the legacy Autogen. I'm modifying an existing library to work on android, and it was made a while ago.

focus my friend and give us details, as I have no understanding how and what runs dotNET on android now.
we can do zoom session if you like too.

[emmauss]

Sorry for the misunderstanding. Let me start from the beginning.
The project I'm porting is https://github.com/unosquare/ffmediaelement . It's currently outdated and uses ffmpeg 4.4 and FFMpeg.Autogen 4 nuget package. As the package, and the other Autogen packages were created using netstandard 2.0, and not multitargeting netstandard and net 5+, the exception I reported occurs because of this

I switched to using https://www.nuget.org/packages/FFmpeg.AutoGen.Bindings.DynamicallyLoaded, updating ffmpeg to 6.0, and setting the resolver manually. This avoids the previous crash, but the Linux resolver doesn't work on android because libdl isn't provided with the android system. This is an issue from android and not dotnet, but the sdk provides ways to dynamically load libraries packaged in your app at runtime. So I made a custom resolver that uses dotnet's NativeLibrary and that works quite well.

internal class AndroidFunctionResolver : FunctionResolverBase
    {
        protected override nint GetFunctionPointer(nint nativeLibraryHandle, string functionName)
        {
            var func = NativeLibrary.GetExport(nativeLibraryHandle, functionName);

            return func;
        }
        protected override string GetNativeLibraryName(string libraryName, int version) => $"lib{libraryName}.so";

        protected override nint LoadNativeLibrary(string libraryName)
        {
            var lib = NativeLibrary.Load(libraryName);

            return lib;
        }
    }

The original project was ported to a cross platform toolkit, so it doesn't rely on wpf. the port isn't public at this moment so I can't share much.

[Ruslan-B]

Well great if you manage to solve the issue, I guess we can close this topic - however would be nice if you share what is behind NativeLibrary call, if some one will try android once again.

[emmauss]

Well great if you manage to solve the issue, I guess we can close this topic - however would be nice if you share what is behind NativeLibrary call, if some one will try android once again.

NativeLibrary is dotnets loader. https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.nativelibrary?source=recommendations&view=net-7.0

[Ruslan-B]

I'll try to address this in upcoming update. Wrt to 7.0 we have another issue #254 - I'll look into it when earlier issues will be solved.